Primary and metastatic human tumor tissues are being studied comparatively to determine if differences can be identified, possibly denoting a shift in cell populations in metastatic tumor. In addition, normal tissue samples and serum are being collected as required. The patients have been clinically followed in order to be able to relate any of these parameters with clinical course. To date, a computerized software system has been developed that allows a monthly printout of patient disease status and survival. Input of our population is current to date. The most interesting laboratory developments thus far are: (1)\the finding of a reduction in tumor plasminogen activator released into media from cultured metastatic cells versus cultured primary, and (2)\the indication that primary tumors which show this reduction are associated with earlier recurrence of disease. A large number of patients have been studied to date, and this appears to be a true finding. In addition, a third finding has been a definite shift in ploidy in some metastatic colon populations as seen by flow cytometry. These three positive findings are being explored and a number of new parameters are being studied. (V)